Editing Lymph node (section)

=== Lymph flow ===
[[File:Lymphatic immune system lymph node5-CROPPED.jpg|thumb|alt=Human lymph node|Labeled diagram of human lymph node showing the flow of [[lymph]]]]
[[File:Illu lymph node structure.png|thumb|300px|Afferent and efferent vessels]]

Lymph enters the convex side of a lymph node through multiple afferent lymphatic vessels, which form a network of lymphatic vessels ({{Langx|la|plexus}}) and flows into a space ({{Langx|la|sinus}}) underneath the capsule called the subcapsular sinus.<ref name="Grays2016" /><ref name=Wheaters2013 /> From here, lymph flows into sinuses within the cortex.<ref name=Wheaters2013 /> After passing through the cortex, lymph then collects in medullary sinuses.<ref name=Wheaters2013 /> All of these sinuses drain into the [[Lymphatic vessel#Efferent vessels|efferent lymphatic vessels]] to exit the node at the hilum on the concave side.<ref name=Wheaters2013 />

These are channels within the node lined by endothelial cells along with fibroblastic reticular cells, allowing for the smooth flow of lymph. The endothelium of the subcapsular sinus is continuous with that of the afferent lymph vessel and also with that of the similar sinuses flanking the trabeculae and within the cortex. These vessels are smaller and do not allow the passage of macrophages so that they remain contained to function within a lymph node. In the course of the lymph, lymphocytes may be activated as part of the [[adaptive immune system|adaptive immune response]].

There is usually only one efferent vessel though sometimes there may be two, in contrast to the multiple afferent channels that bring lymph into the node.<ref>{{cite book |url= https://books.google.com/books?id=2i_ToCBIt8UC&pg=PA201 |title=Histology |last1=Henrikson |first1=Ray C. |last2=Mazurkiewicz |first2=Joseph E. | name-list-style = vanc |date=1 January 1997|publisher=Lippincott Williams & Wilkins|isbn=9780683062250|language=en}}</ref> Medullary sinuses contain [[histiocyte]]s (immobile macrophages) and reticular cells, the former of which, along with T and B cells, become activated in the presence of antigens through lymphatic flow. The fewer efferent vessels allow this flow to be slowed, providing time to activate and distribute a larger number of immune cells in the event of an infection.

A lymph node contains lymphoid tissue, i.e., a meshwork or fibers called ''{{dfn|reticulum}}'' with white blood cells enmeshed in it. The regions where there are few cells within the meshwork are known as ''{{dfn|lymph sinus}}''. It is lined by reticular cells, [[fibroblast]]s and fixed macrophages.<ref name="grays">{{cite book |title=Gray's anatomy |last1=Warwick |first1=Roger| first2 =Peter L. | last2 = Williams | name-list-style = vanc |publisher=Longman|others=illustrated by Richard E. M. Moo re|year=1973|edition=Thirty-fifth |location=London |pages=588–785 |chapter=Angiology (Chapter 6) |orig-year=1858}}</ref>